The positioners are aimed at babies less than six months old and are a way to keep them in a certain position while they sleep. The warning was first issued by the FDA in 2010 over a concern that 12 infant deaths in 13 years had been linked with the use of positioners.

In a letter to manufactures asking them to stop selling the product, the FDA wrote: "Infants placed on their sides in sleep positioning devices are more likely to flip into a face down position rather than onto their backs because their backs are pressed against the side of the infant sleep positioning product. Even if placed properly on their backs, infants may be able to scoot up or downward on the sleep positioning device and risk becoming entrapped and suffocate between the device and the crib side or bassinet."

Multiple companies in the UK — including Tesco, eBay, John Lewis and Mothercare — have decided to ban sleep positioners all together. An eBay spokesperson told Good Housekeeping UK, "Following recent recommendations by US authorities, items of this nature will now be prohibited from being sold on our platform. Our team will be informing sellers and removing any listings that contravene our policies."

The following infant sleep safety guidelines are from the FDA:

NEVER use infant sleep positioners. Using this type of product to hold an infant on his or her side or back is dangerous.

NEVER put pillows, blankets, loose sheets, comforters, or quilts under a baby or in a crib. These products also can be dangerous. Babies don't need pillows and adequate clothing — instead of blankets — can keep them warm.

ALWAYS keep cribs and sleeping areas bare. That means you should also never put soft objects or toys in sleeping areas.

ALWAYS place a baby on his or her back at night and during nap time. An easy way to remember this is to follow the ABCs of safe sleep: "Alone on the Back in a bare Crib."

Rachel Rothman, Chief Technologist in the Good Housekeeping Institute, agrees. "In general, it's always best to keep the bed bare. A crowded sleep environment can lead to injury. Remove pillows, blankets, animals, toys, etc. when infants are sleeping and make sure there is nothing unintended hanging on the crib that the baby can pull and potentially suffocate on. We commend companies like Tesco and Mothercare for taking measures to removing these types of sleep positioners from shelves so that they no longer pose a suffocation risk to babies."